67. Mars Rover Delves Into Crater

After hunkering down for six weeks to ride out a planet-spanning dust storm, the Mars rover Opportunity got back to work in September and began a drive into Victoria Crater, the largest, deepest crater it has yet ­explored. The main research target was a band of white rock just below the rim that may yield clues to the planet’s wetter past.

Enormous dust storms are a fact of life on Mars, and one big enough to blanket the planet occurs every five or six years, says John Callas of NASA, the project manager for Opportunity and its twin, Spirit (currently exploring the other side of Mars). “The rovers were never designed to survive a storm of this magnitude,” Callas says. “The original 90-day mission avoided the usual dust storm season on Mars.”

The rovers’ unexpected longevity has forced their controllers to adapt to Mars dust. They cut back the rovers’ workload sharply to match the little electricity that could be gleaned from the feeble sunlight that filtered through the dim, dusty sky to the rovers’ solar panels. It was a balancing act, though, as the rovers rely in part on waste heat from electrical systems to keep warm: Conserve too much power and the rovers would freeze.

After surviving the storm and, thanks to Martian winds, shedding most of the dust that settled on it, Opportunity began its descent into Victoria Crater. The meteorite impact that produced the crater punched through many geologic layers, each revealing a different chapter of Martian history. Of particular interest is the bright band in the crater wall believed to have been the surface layer at the time of impact.

Callas says that despite the wear on the rover, including an arthritic joint in its robotic arm, Victoria Crater isn’t expected to be Opportunity’s last hurrah. “Within a few kilometers of Victoria are smaller, older craters that might tell us more about Mars’s past,” Callas says. “Opportunity still has a pretty long to-do list.”